| 摘要 |
PROBLEM TO BE SOLVED: To attempt remarkable reduction of nitrogen oxide contained in exhaust gas over a wide temperature range. SOLUTION: An apparatus is constituted so that between an exhaust manifold 3 and an exhaust muffler 4 of an exhaust conduit 2, an oxidation catalyst 5 is arranged on the upstream side of the flow of exhaust gas, a reduction catalysts 6, 7 are arranged on the downstream side, and a hydrocarbon reducing agent is supplied from a space between them by a pump 8. In the oxidation catalyst 5, an active component of platinum or palladium is carried on an alumina carrier. A reduction catalyst is formed in two-stage structure, a reduction catalyst 6 in which at least one kind of active component selected from a group consisting of gold, silver, cobalt, and copper is carried on an alumina carrier are arranged in a preceding stage on the upstream side of the flow of exhausts gas, and a reduction catalyst 7 in which an active component of platinum, rhodium, or indium is carried on an alumina carrier is arranged in a succeeding stage on the downstream side. NO2 , after being converted into NO once, is converted into N2 . |
